Inputs
AIR CONDITIONING PRESSURE TRANSDUCER-PCM INPUTThe Powertrain Control Module (PCM) monitors the A/C compressor discharge (high side) pressure through the air conditioning pressure transducer. The transducer supplies an input to the PCM. The PCM engages the A/C compressor clutch if pressure is sufficient for A/C system operation.
AUTOMATIC SHUTDOWN (ASD) SENSE-PCM INPUT
The ASD sense circuit informs the PCM when the ASD relay energizes. A 12 volt signal at this input indicates to the PCM that the ASD has been activated. This input is used only to sense that the ASD relay is energized.
When energized, the ASD relay supplies battery voltage to the fuel injectors, ignition coils and the heating element in each oxygen sensor. If the PCM does not receive 12 volts from this input after grounding the ASD relay, it sets a Diagnostic Trouble Code (DTC).
BATTERY VOLTAGE-PCM INPUT
The PCM monitors the battery voltage input to determine fuel injector pulse width and generator field control.
If battery voltage is low the PCM will increase injector pulse width (period of time that the injector is energized).
BATTERY TEMPERATURE SENSOR-PCM INPUT
The PCM uses the temperature of the battery area to control the charge rate. The signal is used to regulate the system voltage. The system voltage is higher at cold temperatures and is gradually reduced as temperature around the battery increases.
BRAKE SWITCH-PCM INPUT
When the brake switch is activated, the PCM receives an input indicating that the brakes are being applied. After receiving this input the PCM maintains idle speed to a scheduled RPM through control of the idle air control motor. The brake switch is mounted on the brake pedal support bracket.
CAMSHAFT POSITION SENSOR-PCM INPUT
2.4L Engines
Camshaft Position Sensor-2.4L:
The camshaft position sensor attaches to the rear of the cylinder head.
The sensor also acts as a thrust plate to control camshaft end play.
2.5L Engine
Camshaft Position Sensor-2.5L:
The 2.5L engine is equipped with a camshaft driven mechanical distributor. The distributor is also equipped with an internal camshaft position (fuel sync) sensor.
The PCM determines fuel injection synchronization and cylinder identification from inputs provided by the camshaft position sensor and crankshaft position sensor. From the two inputs, the PCM determines crankshaft position.
Refer to the Camshaft Position Sensor for more information.
CRANKSHAFT POSITION SENSOR-PCM INPUT
2.4L Engines
Camshaft Position Sensor-2.5L:
On 2.4L engines, the second crankshaft counterweight has two sets of four timing reference notches including a 60 degree signature notch. From the crankshaft position sensor input the PCM determines engine speed and crankshaft angle (position).
Crankshaft Position Sensor-2.4L Engines:
The crankshaft position sensor mounts to the engine block behind the generator, just above the oil filter.
2.5L Engine
On a 2.5L engine, this sensor is a hall effect device that detects notches in the flexplate.
Crankshaft Position Sensor-2.5L Engine:
The sensor is located in the transaxle housing, above the vehicle speed sensor.
The PCM determines what cylinder to fire from the crankshaft and camshaft position sensor input. It is also used to synchronize the fuel injectors with their respective cylinders.
Refer to the Crankshaft Position Sensor.
ENGINE COOLANT TEMPERATURE SENSOR-PCM INPUT
Engine Coolant Temperature Sensor-2.4L:
Engine Coolant Temperature Sensor-2.5L:
The coolant sensor threads into the front of the cylinder head 2.4L; next to the coolant fill neck 2.5L. New sensors have sealant applied to the threads.
The coolant temperature sensor has one element. The element supplies coolant temperature signal to the PCM. The PCM supplies coolant temperature information on the CCD Bus to the Body Control Module (BCM) for the instrument panel gauge cluster. The PCM determines engine coolant temperature from the coolant temperature sensor.
As coolant temperature varies, the coolant temperature sensor resistance changes resulting in a different current draw from the PCM.
When the engine is cold, the PCM Will provide slightly richer air-fuel mixtures and higher idle speeds until normal operating temperatures are reached.
FUEL LEVEL SENSOR-PCM INPUT
The fuel level sensor (fuel gauge sending unit) sends a signal to the PCM to indicate fuel level. The purpose of this feature is to prevent a false setting of misfire and fuel system monitor trouble codes if the fuel level is less than approximately 15 percent of its rated capacity. It is also used to send a signal for fuel gauge operation via the PCI bus circuits.
HEATED OXYGEN SENSORS-PCM INPUT
Oxygen Sensor 1/1 Upstream-2.0/2.4L Engines:
Oxygen Sensor 1/1 Upstream-2.5L:
The upstream oxygen sensor threads into the outlet flange of the exhaust manifold.
Oxygen Sensor 1/2 Downstream:
The downstream heated oxygen sensor threads into the outlet pipe at the rear of the catalytic convertor.
As vehicles accumulate mileage, the catalytic convertor deteriorates. The deterioration results in a less efficient catalyst. To monitor catalytic convertor deterioration, the fuel injection system uses two heated oxygen sensors. One sensor upstream of the catalytic convertor, one downstream of the convertor. The PCM compares the reading from the sensors to calculate the catalytic convertor oxygen storage capacity and converter efficiency. Also, the PCM uses the upstream heated oxygen sensor input when adjusting injector pulse width.
When the catalytic converter efficiency drops below emission standards, the PCM stores a diagnostic trouble code and illuminates the malfunction indicator lamp (MIL).
The automatic shutdown relay supplies battery voltage to both the upstream and downstream heated oxygen sensors. The oxygen sensors are equipped with a heating element. The heating elements reduce the time required for the sensors to reach operating temperature.
Oxygen Sensor 1/1 Upstream
The input from the upstream heated oxygen sensor tells the PCM the oxygen content of the exhaust gas. Based on this input, the PCM fine tunes the air-fuel ratio by adjusting injector pulse width.
The sensor input switches from 0 to 1 volt, depending upon the oxygen content of the exhaust gas in the exhaust manifold. When a large amount of oxygen is present (caused by a lean air-fuel mixture), the sensor produces voltage as low as 0.1 volt. When there is a lesser amount of oxygen present (rich air-fuel mixture) the sensor produces a voltage as high as 1.0 volt. By monitoring the oxygen content and converting it to electrical voltage, the sensor acts as a rich-lean switch.
The heating element in the sensor provides heat to the sensor ceramic element. Heating the sensor allows the system to enter into closed loop operation sooner. Also, it allows the system to remain in closed loop operation during periods of extended idle.
In Closed Loop, the PCM adjusts injector pulse width based on the upstream heated oxygen sensor input along with other inputs. In Open Loop, the PCM adjusts injector pulse width based on preprogrammed (fixed) values and inputs from other sensors.
Oxygen Sensor 1/2 Downstream
The downstream heated oxygen sensor input is used to detect catalytic convertor deterioration. As the convertor deteriorates, the input from the downstream sensor begins to match the upstream sensor input except for a slight time delay. By comparing the downstream heated oxygen sensor input to the input from the upstream sensor, the PCM calculates catalytic convertor efficiency.
IGNITION SENSE-PCM INPUT
The ignition sense input informs the Powertrain Control Module (PCM) that the ignition switch is in the crank or run position.
INTAKE AIR TEMPERATURE SENSOR-PCM INPUT
Intake Air Temperature Sensor and MAP Sensor-2.0L:
The IAT sensor and Manifold Absolute Pressure (MAP) sensor are a combined sensor that attach to the intake manifold for 2.0L engine.
Intake Air Temperature Sensor and MAP Sensor-2.4L:
Intake Air Temperature Sensor and MAP Sensor-2.5L:
The IAT sensor threads into the intake manifold for the 2.4/2.5L engines.
The Intake Air Temperature (IAT) sensor measures the temperature of the intake air as it enters the engine. The sensor supplies one of the inputs the PCM uses to determine injector pulse width and spark advance.
KNOCK SENSOR-PCM INPUT (2.0L/2.4L ENGINES)
Knock Sensor:
The knock sensor threads into the side of the cylinder block in front of the starter.
When the knock sensor detects a knock in one of the cylinders, it sends an input signal to the PCM. In response, the PCM retards ignition timing for all cylinders by a scheduled amount.
Knock sensors contain a piezoelectric material which sends an input voltage (signal) to the PCM. As, the intensity of the engine knock vibration increases, the knock sensor output voltage also increases.
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR-PCM INPUT
Intake Air Temperature Sensor and MAP Sensor-2.0L:
Intake Air Temperature Sensor and MAP Sensor-2.4L:
Intake Air Temperature Sensor and MAP Sensor-2.5L:
The MAP sensor mounts to the intake manifold.
The PCM supplies 5 volts direct current to the MAP sensor. The MAP sensor converts intake manifold pressure into voltage. The PCM monitors the MAP sensor output voltage. As vacuum increases, MAP sensor voltage decreases proportionately. Also, as vacuum decreases, MAP sensor voltage increases proportionately.
At key on, before the engine is started, the PCM determines atmospheric air pressure from the MAP sensor voltage. While the engine operates, the PCM determines intake manifold pressure from the MAP sensor voltage. Based on MAP sensor voltage and inputs from other sensors, the PCM adjusts spark advance and the air/fuel mixture.
POWER STEERING PRESSURE SWITCH-PCM INPUT
A pressure sensing switch is located on the power steering gear.
Power Steering Pressure Switch:
The switch provides an input to the PCM during periods of high pump load and low engine RPM; such as during parking maneuvers.
When power steering pump pressure exceeds 4137 kPa (600 psi), the switch is open. The PCM increases idle air flow through the IAC motor to prevent engine stalling. When pump pressure is low, the switch is closed.
SENSOR RETURN-PCM INPUT
The sensor return circuit provides a low electrical noise ground reference for all of the systems sensors. The sensor return circuit connects to internal ground circuits within the Powertrain Control Module (PCM).
SPEED CONTROL-PCM INPUT
The speed control system provides five separate voltages (inputs) to the Powertrain Control Module (PCM). The voltages correspond to the ON, OFF; SET, RESUME, CANCEL, and DECEL.
The speed control ON voltage informs the PCM that the speed control system has been activated. The speed control SET voltage informs the PCM that a fixed vehicle speed has been selected. The speed control RESUME voltage indicates the previous fixed speed is requested. The speed control CANCEL voltage tells the PCM to deactivate but retain set speed in memory (same as depressing the brake pedal). The speed control DECEL voltage informs the PCM to coast down to a new desired speed. The speed control OFF voltage tells the PCM that the speed control system has deactivated. Refer to the Speed Control for more speed control information.
SCI RECEIVE-PCM INPUT
SCI Receive is the serial data communication receive circuit for the DRB scan tool. The Powertrain Control Module (PCM) receives data from the DRB through the SCI Receive circuit.
TRANSAXLE PARK/NEUTRAL SWITCH-PCM INPUT
Park Neutral Switch-4 Speed Electronic Automatic Transaxle-Typical:
The park/neutral switch is located on the transaxle housing.
It provides an input to the PCM indicating whether the automatic transaxle is in Park or Neutral. This input is used to determine idle speed (varying with gear selection) and ignition timing advance. The park neutral switch is sometimes referred to as the neutral safety switch.
THROTTLE POSITION SENSOR-PCM INPUT
Throttle Position Sensor-2.0/2.4L Engines:
Throttle Position Sensor-2.5L Engine:
The throttle position sensor mounts to the side of the throttle body.
The Throttle Position Sensor (TPS) connects to the throttle blade shaft. The TPS is a variable resistor that provides the PCM with an input signal (voltage). The signal represents throttle blade position. As the position of the throttle blade changes, the resistance of the TPS changes.
The PCM supplies approximately 5 volts DC to the TPS. The TPS output voltage (input signal to the PCM) represents throttle blade position. The TPS output voltage to the PCM varies from approximately 0.5 volt at minimum throttle opening (idle) to a maximum of 3.7 volts at wide open throttle.
Along with inputs from other sensors, the PCM uses TPS input to determine current engine operating conditions. The PCM also adjusts fuel injector pulse width and ignition timing based on these inputs.
VEHICLE SPEED AND DISTANCE-PCM INPUT
Park Neutral Switch-4 Speed Electronic Automatic Transaxle-Typical:
The transaxle output speed sensor supplies the vehicle speed and distance inputs to the PCM. The output speed sensor is located on the side of the transaxle.
The speed and distance signals, along with a closed throttle signal from the TPS, determine if a closed throttle deceleration or normal idle condition (vehicle stopped) exists. Under deceleration conditions, the PCM adjusts the idle air control motor to maintain a desired MAP value. Under idle conditions, the PCM adjusts the idle air control motor to maintain a desired engine speed.